Human Anatomy Vol 1

Superior

intercostal artery

Posterior

intercostal vein

Tubercle - -

-- Ventral ramus of C8

--- Ventral ramus of T1

Scalenus medius

Serratus anterior

BONES AND JOINTS OF THORAX

The first rib ossifies from one primary centre for the

shaft and only two secondary centres, one for the

head and the other for the tubercle. Otherwise its

ossification is similar to that of a typical rib.

Second Rib

F*sfures

The features of the second rib are:

1 The length is twice that of the first rib.

(^2) The shaft is sharply curved, like that of the first rib.
3 The non-articular part of the tubercle is small.
4 The angle is slight ancl is situated close to the
tubercle.
5 The shaft has no twist. The outer surface is convex
and faces more upwards than outwards. Near its
middle it is marked by alarge rough tubercle. This
tubercle is a unique feature of the second rib. The
inner surface of the shaft is smooth and concave. It
faces more downwards than inwards. There is a
short costal E;roove on the posterior part of this
surface.
The posterior part of the upper border has distinct
outer and inner lips. The part of the outer lip just in
front of the angle is rough.
Affscfuncer?fs
(^1) The rough tubercle on the outer surface gives origin
to one and a half digitations of the serratus anterior
muscle.
2 The rough part of the upper border receives the
insertion of the scalenus posterior.
Ienth Rib
The tenth rib closely resembles a typical rib, but is
(^1) Shorter.
(^2) Has only a single facet on the head, for the body of
the tenth thoracic vertebra.
Elevenlh ond Tweltth Ribs
Eleventh and twelfth ribs are short. They have pointed
ends. The necks and tubercles are absent. The angle and
costal groove are poorly marked in the eleventh rib;
and are absent in the twelfth rib.
Atfecfirnent CInd ReCsfisns of the
1 The capsular and radiate ligaments are attached to
the head of the rib (Fig. 13.6).
2 The following are attached on the inner surface.
a. The quadratus lumborum is inserted on the lower
part of the medial half to two-thirds of this surface
(Fig. 13.8a).
Costal cadilage
Fig. 13.7: Superior view of the Iirst rib (left
(^2) Superiorly, the neck is related to:
a. The deep cervical vessels.
b. The eighth cervical nerve.
The anterior groove on the superior surface of the
shaft lodges the subclavian vein, and the posterior
groove lodges the subclavian artery and the lower
trunk of the brachial plexus.
The structures attached to the upper surface of the
shaft are:
a. The origin of the subclavius muscle at the anterior
end.
b. The attachment of the costoclavicular ligament at
the anterior end behind the subclavius.
c. The insertion of the scalenus anterior on the
scalene tubercle.
d. The insertion of the scalenus medius on the
elongated rough area behind the groove for the
subclavian aitery.
The lower surface of the shaft is covered by costal
pleura and is related near its outer border to the small
first intercostal nerve which is very small.
The outer border gives origin to:
The external intercostal muscle, and
The upper part of the first digitation of the serratus
anterior, just behind the groove for the subclavian
artery. The thick portion of the outer border is
covered by the scalenus posterior.
The inner border gives attachment to the supra-
pleural membrane.
The tubercle gives attachment to the lateral
costotransverse ligament.
Sympathetic chain
lnner border
Scalene tubercle for-
scalenus anterior
Outer border
Lower trunk of
brachial plexus
Groove for
subclavian artery
Groove for
subclavian vein
Subclavius muscle
Costoclavicular
ligament
side)
a.
b.